Ignition Problems-Starting..or not??

My brother is having a problem starting his 1985 F150 pick up. He has a 4.9L inline 6cyl engine. It is a standard, and kind of a low end pick up. The problem he is having is that sometimes the truck just will not start. It can start fine for days, then when he turns it off for a couple of minutes or comes out in the morning he is unable to start the truck. It does not seem to matter if the truck is cold or hot, or has just ran or sat overnight. In other words, there does not seem to be a pattern as to when it will or will not start. The truck turns over, and the battery is strong, everything fine there. Seems to be no spark, but there is fuel. We have replaced the coil, and the ignition control module with no success. The solenoid for the starter was replaced previously, due to no start, and no cranking of engine starter. It has been suggested that possibly the "ignition pick up coil" in the distributor could be the problem. I am wondering if anyone has any experience with this and could advise if we are on the right track. Engine turns over fine, and there is fuel, but no spark and the engine does not seem to "catch" when cranking over. Has anyone had a similar experience or any thoughts as to what the problem might be, please post me a message.

Brian